feat(third_party/bazel): Check in rules_haskell from Tweag

third_party/bazel/rules_haskell/tests/ghc.nix

@@ -0,0 +1,41 @@
+{ pkgs ? import ../nixpkgs {}
+# Whether we want to wrap the packages using <bazel_haskell_wrapper>.
+# When this is called from inside bazel, we need to wrap the haskell package
+# set using <bazel_haskell_wrapper>. Otherwise we don't need (and don't want)
+# to.
+, wrapPackages ? (builtins.tryEval <bazel_haskell_wrapper>).success
+}:
+
+with pkgs;
+
+let haskellPackages = pkgs.haskell.packages.ghc864.override {
+      overrides = with pkgs.haskell.lib; self: super: rec {
+        libc = import ./haddock/libC.nix self pkgs;
+      };
+    };
+    genBazelBuild =
+      if wrapPackages
+      then callPackage <bazel_haskell_wrapper> {}
+      else (x: x);
+
+in
+  {
+  ghc = haskellPackages.ghcWithPackages (p: with p; [
+
+    # haskell_proto_library inputs
+    bytestring
+    containers
+    data-default-class
+    lens-family
+    lens-labels
+    proto-lens
+    text
+
+  # test inputs
+  libc
+
+  # for test runner
+  hspec
+  ]);
+  haskellPackages = genBazelBuild haskellPackages;
+}